All-glass solar vacuum tube, connecting with water tank or manifold, when it works, cold water flows down into the vacuum tube, and there it is heated with solar energy absorbed by the coating outside of inner vacuum tube, the solar will be absorbed efficiently by the coating with little loss of heat because of the vacuum between the inner and outer glass tubes, and when cold water becomes hot, hot water will rise up to water tank or manifold because of the larger proportion to cold water, cold water again flows into solar vacuum tube for another heating process.